1. Field of the Invention
The present invention relates to a method of manufacturing a slider of a thin-film magnetic head which comprises a medium facing surface that faces toward a recording medium and a thin-film magnetic head element located near the medium facing surface.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as areal recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a recording head having an induction magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading. MR elements include an anisotropic magnetoresistive (AMR) element that utilizes the AMR effect and a giant magnetoresistive (GMR) element that utilizes the GMR effect. A reproducing head using an AMR element is called an AMR head or simply an MR head. A reproducing head using a GMR element is called a GMR head. An AMR head is used as a reproducing head where areal density is more than 1 gigabit per square inch. A GMR head is used as a reproducing head where areal density is more than 3 gigabits per square inch. It is GMR heads that have been most widely used recently.
The performance of the reproducing head is improved by replacing the AMR film with a GMR film and the like having an excellent magnetoresistive sensitivity. Alternatively, a pattern width such as the reproducing track width and the MR height, in particular, may be optimized. The MR height is the length (height) between an end of the MR element located in the air bearing surface and the other end. The air bearing surface is a surface of the thin-film magnetic head facing toward a magnetic recording medium.
Performance improvements in a recording head are also required as the performance of a reproducing head is improved. It is required to increase the linear density in order to increase the areal density among the performance characteristics of the recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein the width of top and bottom poles sandwiching the recording gap layer on a side of the air bearing surface is reduced down to microns or a submicron order. This width is one of the factors that determine the recording head performance. Semiconductor process techniques are utilized to implement such a structure. Another factor is a pattern width such as the throat height, in particular. The throat height is the length (height) of pole portions, that is, portions of magnetic pole layers facing each other with a recording gap layer in between, between the air-bearing-surface-side end and the other end. A reduction in throat height is desired in order to improve the recording head performance. The throat height is controlled by an amount of lapping when the air bearing surface is processed.
As thus described, it is important to fabricate well-balanced recording and reproducing heads to improve the performance of the thin-film magnetic head.
In order to implement a thin-film magnetic head that achieves high recording density, the requirements for the reproducing head include a reduction in reproducing track width, an increase in reproducing output, and a reduction in noise. The requirements for the recording head include a reduction in recording track width, an improvement in overwrite property that is a parameter indicating one of characteristics when data is written over existing data, and an improvement in nonlinear transition shift (NLTS).
In general, a flying-type thin-film magnetic head used in a hard disk device and the like is made up of a slider, a thin-film magnetic head element being formed at the trailing edge of the slider. The slider slightly floats over a recording medium by means of the airflow generated by the rotation of the medium.
Reference is now made to FIG. 23A to FIG. 26A, FIG. 23B to FIG. 26B, and FIG. 27 to describe an example of a manufacturing method of a related-art thin-film magnetic head element. FIG. 23A to FIG. 26A are cross sections each orthogonal to the air bearing surface. FIG. 23B to FIG. 26B are cross sections of the pole portion each parallel to the air bearing surface.
According to the manufacturing method, as shown in FIG. 23A and FIG. 23B, an insulating layer 102 made of alumina (Al2O3), for example, having a thickness of about 5 to 10 xcexcm, is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. Next, on the insulating layer 102, a bottom shield layer 103 made of a magnetic material is formed for a reproducing head.
Next, a bottom shield gap film 104 made of an insulating material such as alumina and having a thickness of 100 to 200 nm, for example, is formed through sputtering on the bottom shield layer 103. On the bottom shield gap film 104, an MR element 105 for reproduction having a thickness of tens of nanometers is formed. Next, a pair of electrode layers 106 are formed on the bottom shield gap film 104. The electrode layers 106 are electrically connected to the MR element 105.
Next, a top shield gap film 107 made of an insulating material such as alumina is formed through sputtering, for example, on the bottom shield gap film 104, the MR element 105 and the electrode layers 106. The MR element 105 is embedded in the shield gap films 104 and 107.
Next, on the top shield gap film 107, a top-shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description) 108 is formed. The bottom pole layer 108 has a thickness of about 3 xcexcm and is made of a magnetic material and used for both the reproducing head and the recording head.
Next, as shown in FIG. 24A and FIG. 24B, a recording gap layer 109 made of an insulating film such as an alumina film and having a thickness of 0.2 xcexcm is formed on the bottom pole layer 108. Next, the recording gap layer 109 is partially etched to form a contact hole 109a for making a magnetic path. Next, a top pole tip 110 for the recording head is formed on the recording gap layer 109 in the pole portion. The top pole tip 110 is made of a magnetic material and has a thickness of 0.5 to 1.0 xcexcm. At the same time, a magnetic layer 119 made of a magnetic material is formed for making the magnetic path in the contact hole 109a for making the magnetic path.
Next, as shown in FIG. 25A and FIG. 25B, the recording gap layer 109 and the bottom pole layer 108 are etched through ion milling, using the top pole tip 110 as a mask. As shown in FIG. 25B, the structure is called a trim structure wherein the sidewalls of the top pole portion (the top pole tip 110), the recording gap layer 109, and a part of the bottom pole layer 108 are formed vertically in a self-aligned manner.
Next, an insulating layer 111 of alumina, for example, having a thickness of about 3 Jim is formed over the entire surface. The insulating layer 111 is polished to the surfaces of the top pole tip 110 and the magnetic layer 119 and flattened.
On the flattened insulating layer 111 a first layer 112 of a thin-film coil is made for the induction-type recording head. The thin-film coil 112 is made of copper (Cu), for example. Next, a photoresist layer 113 is formed into a specific shape on the insulating layer 111 and the first layer 112 of the coil. Heat treatment is performed at a specific temperature to flatten the surface of the photoresist layer 113. Next, a second layer 114 of the thin-film coil is formed on the photoresist layer 113. Next, a photoresist layer 115 is formed into a specific shape on the photoresist layer 113 and the second layer 114 of the coil. Heat treatment is performed at a specific temperature to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 26A and FIG. 26B, a top pole layer 116 for the recording head is formed on the top pole tip 110, the photoresist layers 113 and 115 and the magnetic layer 119. The top pole layer 116 is made of a magnetic material such as Permalloy (NiFe). Next, an overcoat layer 117 of alumina, for example, is formed to cover the top pole layer 116. Finally, machine processing of the slider including the forgoing layers is performed to form the air bearing surface 118 of the thin-film magnetic head including the recording head and the reproducing head. The thin-film magnetic head element is thus completed.
FIG. 27 is a top view of the thin-film magnetic head element shown in FIG. 26A and FIG. 26B. The overcoat layer 117 and the other insulating layers and film are omitted in FIG. 27.
Reference is now made to FIG. 28 to FIG. 30 to describe the configuration of the slider and a method of manufacturing the same. FIG. 28 is a bottom view that illustrates an example of the configuration of the air bearing surface of the slider. As shown, the air bearing surface of the slider 120 is shaped such that the slider 120 slightly floats over a recording medium such as a magnetic disk by means of the airflow generated by the rotation of the medium. In FIG. 28 numeral 121a indicates a convex portion and numeral 121b indicates a concave portion. A thin-film magnetic head element 122 is located near the air-outflow-side end of the air bearing surface of the slider 120 (that is, on the upper side of FIG. 28). The configuration of the head element 122 is shown in FIG. 26A and FIG. 26B, for example. Portion C of FIG. 28 corresponds to FIG. 26B.
The slider 120 is fabricated as follows. A wafer includes a plurality of rows of portions to be sliders (hereinafter called slider portions) each of which includes the thin-film magnetic head element 122. This wafer is cut in one direction to form blocks called bars each of which includes a row of slider portions. Each of the bars is then lapped to form the air bearing surface. Furthermore, the convex portion 121a and the concave portion 121b are formed. Each of the bars is then divided into sliders 120.
FIG. 29 is a cross-sectional view taken along line 29-29 of FIG. 28. FIG. 29 illustrates only the main part of the thin-film magnetic head element 122. As shown, the greater part of the slider 120 is made up of the substrate 101 of aluminum oxide and titanium carbide, for example. The rest of the slider 120 is made up of the insulating layer 127 of alumina, for example, and the head element 122 and so on formed in the insulating layer 127. The greater part of the insulating layer 127 is the overcoat layer 117.
As disclosed in Published Unexamined Japanese Patent Application Hei 9-63027 (1997), for example, a protection film of a material such as diamond-like carbon (DLC) may be formed on the air bearing surface of the slider 120 in order to prevent corrosion, for example, of the bottom shield layer 103, the bottom pole layer 108, the top pole tip 110, and the top pole layer 116 and so on. FIG. 30 is a cross-sectional view that illustrates the slider 120 with a protection film 128 formed on the air bearing surface, the slider 120 slightly floating over a recording medium 140.
In order to improve the performance characteristics of a hard disk device, such as areal recording density, a method of increasing linear recording density and a method of increasing track density may be taken. To design a high-performance hard disk device, specific measures taken for implementing the recording head, the reproducing head or the thin-film magnetic head as a whole depend on whether linear recording density or track density is emphasized. That is, if priority is given to track density, a reduction in track width is required for both recording head and reproducing head, for example.
If priority is given to linear recording density, it is required for the reproducing head to improve the reproducing output and to reduce the half width of the reproducing output. Moreover, it is required to reduce the distance between the hard disk platter and the slider (hereinafter called a magnetic space). To achieve areal density of 20 to 30 gigabits per square inch, a magnetic space of 15 to 25 nm, for example, is required.
A reduction in magnetic space is achieved by reducing the amount of floating of the slider. A reduction in magnetic space not only contributes to an improvement in the reproducing output and a reduction in the half width of the reproducing output of the reproducing head, but also to an improvement in the overwrite property of the recording head.
The following is a description of the problem that arises when the magnetic space is reduced. In the prior art, lapping of the air bearing surface of the slider 120 has been performed on a rotating tin surface plate through the use of diamond slurry, for example.
A plurality of materials that make up the slider 120 have different hardnesses. For example, a comparison is made between: aluminum oxide and titanium carbide that is a ceramic material used for the substrate 101; a magnetic material such as NiFe used for the bottom shield layer 103, the bottom pole layer 108, the top pole tip 110, the top pole layer 116 and so on; and alumina used for the insulating layer 127. The hardness of aluminum oxide and titanium carbide is the greatest while that of NiFe is the smallest. The hardness of alumina is smaller than that of aluminum oxide and titanium carbide, and greater than that of NiFe.
The slider 120 includes a plurality of layers having different hardnesses as thus described. If this slider 120 is lapped on a tin surface plate through the use of diamond slurry as an abrasive, differences in level may result among the layers having different hardnesses. For example, as shown in FIG. 29, a difference of about 1 to 2 nm in level is created between the insulating layer 127 and the top pole layer 116, for example, that is a layer made of a magnetic material such as NiFe, an end of the top pole layer 116 being located behind an end of the insulating layer 127. A difference of about 4 to 5 nm in level is created between the insulating layer 127 and the substrate 101, an end of the insulating layer 127 being located behind an end of the substrate 101. In this case, the difference in level is about 5 to 7 nm between the surface of the thin-film magnetic head element 122 closer to the air bearing surface and the surface of the substrate 101 closer to the air bearing surface, the protection film 128 being excluded.
If the thickness of the protection film 128 is 5 nm, as shown in FIG. 30, the difference in level is about 10 to 12 nm between the surface of the head element 122 closer to the air bearing surface and the surface of a portion of the protection film 128 that corresponds to the substrate 101, the surface being located in the air bearing surface. If the distance between the slider 120 and the recording medium 140 when the slider 120 is flying is 10 nm, the magnetic space, that is, the distance between the medium 140 and the surface of the head element 122 closer to the air bearing surface when the slider 120 is flying, is about 20 to 22 nm. When the magnetic space is of such a degree, attainable areal density is limited to about 30 gigabits per square inch.
As thus described, the related-art thin-film magnetic head may have a difference in level in the air bearing surface of the slider 120, the portion corresponding to the head element 122 being recessed behind the other part. As a result, it is difficult to reduce the magnetic space, and to improve the recording density.
Since it is difficult to reduce the magnetic space of the related-art thin-film magnetic head as described above, it is impossible to improve the performance of the reproducing head in particular to a sufficient degree, such as an improvement in the reproducing output and a reduction in half width of the reproducing head. As a result, the problem of the related art is that the error rate of the hard disk devices for high density recording increases and the yield of the hard disk devices decreases.
In Published Unexamined Japanese Patent Application Hei 8-339511 (1996), a method of manufacturing sliders is disclosed wherein the step of lapping the air bearing surfaces of the sliders is performed such that an insulator surrounding the member making up each thin-film magnetic head element is eroded in a more uneven manner, compared to the member making up the head element, so as to make the member protrude further than the insulator.
In this technique, however, a great difference in level is created in the air bearing surface of the slider between the insulator and the member in particular. It is therefore required to form an unnecessarily thick protection film to reduce this difference in level.
Another problem is that, if the magnetic space is reduced, the slider is likely to collide with the recording medium, and damage to the medium frequently results. To avoid this, it is required to enhance the smoothness of the surface of the medium. However, the slider easily sticks to the medium if the smoothness of the surface of the medium is enhanced.
To solve this problem, techniques are disclosed in Published Unexamined Japanese Patent Application Hei 8-287440 (1996), Published Unexamined Japanese Patent Application Hei 8-293111 (1996), and Published Unexamined Japanese Patent Application Hei 11-120528 (1999), wherein a protrusion is provided on the medium facing surface of the slider to prevent the slider from sticking to the surface of the medium. In Published Unexamined Japanese Patent Application Hei 7-230615 (1995), a technique is disclosed to flatten the flying surface of the slider, wherein a protection film made of an insulating film is provided in a recess produced between the slider and the head element when the flying surface of the slider is processed. In this publication the following first and second methods are disclosed to provide the protection film in the recess. The first method is to form a protection film through sputtering over the entire surface including the flying surface of the slider and a surface of the head element located closer to the flying surface, and to lap the flying surface of the slider so as to remove a portion of the protection film on the flying surface of the slider. The second method is to form a photosensitive organic film over the entire surface including the flying surface of the slider and a surface of the head element located closer to the flying surface; then to expose only a portion of the organic film on the surface of the head element; and then to remove the portion of the organic film. A protection film is then formed over the entire surface through sputtering, and the rest of the organic film is finally removed.
However, the technique disclosed in Published Unexamined Japanese Patent Application Hei 7-230615 has a problem that, although the flying surface, that is, the medium facing surface of the slider is flattened, it is difficult to obtain a desired shape of the medium facing surface of the slider, such as a shape in which the above-mentioned protrusion is provided on the medium facing surface.
In Published Unexamined Japanese Patent Application Hei 11-185418 (1999), a technique is disclosed to prevent the slider from sticking to the recording medium, wherein a convexity is formed on the air inflow side of the air bearing surface of the slider, and the corners of the air outflow end are removed, such that the air bearing surface forms a specific angle (but not parallel) with respect to the recording medium when the medium is at rest.
In this technique, however, although it is possible to prevent the slider from sticking to the medium, it is impossible to eliminate the difference in level in the air bearing surface between the portion corresponding to the head element and the other part. It is therefore difficult to reduce the magnetic space.
It is an object of the invention to provide a method of manufacturing a slider of a thin-film magnetic head for achieving low-flying sliders, and for obtaining a desired shape of the medium facing surface of the slider.
A method of the invention is provided for manufacturing a slider of a thin-film magnetic head, the slider including a medium facing surface that faces toward a recording medium and a thin-film magnetic head element located near the medium facing surface. The method comprises the steps of forming the medium facing surface in a material used for making the slider, the material including the head element; and etching at least a part of the medium facing surface, such that a reduction is made in difference in level between a portion of the medium facing surface corresponding to the head element and the rest of the medium facing surface, or such that the portion of the medium facing surface corresponding to the head element is located closer to the recording medium than at least a portion of the rest of the medium facing surface.
According to the method of the invention, at least a part of the medium facing surface is etched. As a result, a reduction is achieved in difference in level between the portion of the medium facing surface of the slider corresponding to the head element and the rest of the medium facing surface. Alternatively, the portion of the medium facing surface is located closer to the recording medium than at least a portion of the rest of the medium facing surface.
According to the method of the invention, the step of forming the medium facing surface may include lapping of a surface of the material to be the medium facing surface.
The method of the invention may further comprise the step of forming a protection film over the medium facing surface after the step of etching. In this case, the protection film may be made of diamond-like carbon. The method of the invention may further comprise the step of forming a convex portion on the protection film.
The method of the invention may further comprise the step of forming a protection film over the medium facing surface after the step of forming the medium facing surface, wherein a portion of the protection film is etched in the step of etching. In this case, the protection film may be made of diamond-like carbon. The protection film may have a thickness greater than or equal to the difference in level between the portion of the medium facing surface before undergoing the step of etching, the portion corresponding to the head element, and at least a portion of the rest of the medium facing surface.
According to the method of the invention, a convex portion may be formed on the rest of the medium facing surface in the step of etching.
According to the method of the invention, ion milling or reactive ion etching may be used in the step of etching.
According to the method of the invention, etching may be performed through the use of focused ion beam in the step of etching. In this case, alignment of the focused ion beam may be made with reference to an end of the medium facing surface in the step of etching.
According to the method of the invention, in the step of etching with the focused ion beam, the medium facing surface may be shaped such that a portion thereof between an air-inflow-side end and an air-outflow-side end projects further toward the recording medium. In this case, in the step of etching with the focused ion beam, the medium facing surface may be shaped such that an arc is formed between the air-inflow-side end and the air-outflow-side end.
According to the method of the invention, the head element may include a magnetoresistive element, and the length of the magnetoresistive element between an end thereof located in the medium facing surface and the other end may be controlled in the step of etching with the focused ion beam.
According to the method of the invention, the head element may include: a first magnetic layer and a second magnetic layer magnetically coupled to each other each of which includes at least one layer, the first and second magnetic layers including magnetic pole portions opposed to each other and placed in regions on a side of the medium facing surface; a gap layer placed between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the magnetic layers and insulated from the magnetic layers. In addition, the length of the pole portions between an end thereof located in the medium facing surface and the other end may be controlled in the step of etching with the focused ion beam.
Other and further objects, features and advantages of the invention will appear more fully from the following description.